It seems to have so far escaped OSNews' notice (if the top few hits for a site-search for 'Steam' is any indication) that Steam for Linux is now in Open Beta; you can get the Linux steam client from steampowered.com. So far, they appear to only be making an Ubuntu .deb available, and the client will require closed-source GPU drivers in order to work.

Meanwhile the overall desktop market for discrete GPU's keeps shrinking, people find that they get good enough performance for their needs from the built-in graphics solutions which keep improving quite rapidly with each new hardware generation.